Many image systems exist that employ local or remote non-destructive sensing of spectrally dependent properties of substances for identifying the presence of one or more substances. These substances could include, for example, gases, chemicals, minerals, pollutants, and objects both man-made and natural in the form of a gas, liquid or solid. Examples of local sensing and identifying methods that have been used to detect spectral properties include ion mobility spectrometry, flame photometry, mass spectrometry, electrochemistry, detection paper methods, surface acoustic wave methods, laser-induced breakdown spectroscopy, photo ionization detection, gas chromatography and cavity-ring-down spectroscopy. Local sensing and identifying systems and methods are limited by the ability to retrieve a sample or locate detection equipment near a target area.
Furthermore, it is often desirable to know from a distance the presence of dangerous agents, substances or devices near a target area. For example, in modern warfare, explosives, such as individual improvised explosive devices or entire weapon manufacturing sites, leave a chemical residue and/or chemical plume. It is generally unknown what chemical agents are present in the chemical residue and/or chemical plume and what type of target may be hidden behind the target surface. It is also desirable to know from a distance what agents might be present due to a chemical fire or spill. Though these are merely exemplary, it is understood that it is generally desirable to know the agents and substances in contaminates associated with a remote target or region before any individual comes in contact with or in close proximity to the remote target or region.